<template>
  <div class="spec-preview">
    <img
      src="https://imgservice.suning.cn/uimg1/b2c/atmosphere/g7UNqmuqkPqrWSrxnzSW4w.png_800w_800h_4e"
      ref="big"
    />
    <!-- 显示放大的图片 -->
    <div class="event" @mousemove="handleMove"></div>
    <div class="big">
      <img
        src="https://imgservice.suning.cn/uimg1/b2c/atmosphere/g7UNqmuqkPqrWSrxnzSW4w.png_800w_800h_4e"
        ref="showImg"
      />
    </div>
    <!-- 遮罩层 -->
    <div class="mask" ref="mask"></div>
  </div>
</template>

<script>
export default {
  name: "myZoom",
  methods: {
    handleMove(e) {
      const mask = this.$refs.mask;
      const big = this.$refs.big;
      const showImg = this.$refs.showImg;
      // 遮罩左值和顶部值
      let left = e.offsetX - mask.offsetWidth / 2;
      let top = e.offsetY - mask.offsetHeight / 2;
      // 判断方位超出情况
      if (left < 0) {
        left = 0;
      } else if (left >= big.clientWidth - mask.clientWidth) {
        left = big.clientWidth - mask.clientWidth;
      }
      if (top < 0) {
        top = 0;
      } else if (top >= big.clientHeight - mask.clientHeight) {
        top = big.clientHeight - mask.clientHeight;
      }
      const scalex = showImg.clientWidth / big.clientWidth;
      const scaley = showImg.clientHeight / big.clientHeight;

      mask.style.left = left + "px";
      mask.style.top = top + "px";
      showImg.style.left = -scalex * left + "px";
      showImg.style.top = -scaley * top + "px";
    },
  },
};
</script>

<style lang="less" scoped>
.spec-preview {
  position: relative;
  width: 400px;
  height: 350px;
  border: 1px solid #ccc;

  img {
    width: 100%;
    height: 100%;
  }

  .event {
    width: 100%;
    height: 100%;
    position: absolute;
    top: 0;
    left: 0;
    z-index: 99;
  }

  .mask {
    width: 50%;
    height: 50%;
    background-color: rgba(0, 255, 0, 0.3);
    position: absolute;
    left: 0;
    top: 0;
    display: none;
  }

  .big {
    width: 100%;
    height: 100%;
    position: absolute;
    top: -1px;
    left: 100%;
    border: 1px solid #aaa;
    overflow: hidden;
    z-index: 99;
    display: none;
    background: white;

    img {
      width: 200%;
      max-width: 200%;
      height: 200%;
      position: absolute;
      left: 0;
      top: 0;
    }
  }

  .event:hover ~ .mask,
  .event:hover ~ .big {
    display: block;
  }
}
</style>
